This invention relates to a method of forming electrodes on a dielectric resonator part, and more particularly to a method of forming input and output electrodes on the outer peripheral surface of a dielectric block during the production process of a dielectric resonator part comprising a dielectric block having at least one dielectric coaxial resonator.
FIGS. 5(a), 5(b) and 5(c) show a prior art process for forming input and output electrodes on a dielectric resonator part. First, a dielectric block 1 is prepared which is approximately a rectangular parallelopiped in shape. As shown in FIG. 5(a), two throughholes 2 and 3 are formed through the block 1 connecting its front surface 1a with its back surface 1b, and a pair of resist films 4 and 5, each configured in the shape of a frame, is formed on the outer peripheral surface of the block 1 by a screen printing or padding method, one of them (indicated by numeral 4) extending over the upper surface 1c of the block 1 and its right-hand side surface 1d and the other of them (indicated by numeral 5) extending over the upper surface 1c and the left-hand side surface 1e. Next, as shown in FIG. 5(b), an electrically conductive film 6 is formed all over the external surface of the dielectric block 1 and the entire inner surfaces of the throughholes 2 and 3 are coated with an electrically conductive material (referred to as inner conductors 7 and 8, respectively). Next, as shown in FIG. 5(c), the resist films 4 and 5 are removed from the dielectric block 1. Accordingly, frame-shaped areas 1f and 1g on the outer periphery of the block 1, which were under the resist films 4 and 5, become exposed to the exterior, and the conductive film 6 covering the external surface of the block 1 becomes divided into three mutually separated parts, that is, an input electrode 10, an output electrode 11 and the remainder which will be referred to as the outer conductor 9.
Thereafter, annular portions of the inner conductors 7 and 8 with a specified width are removed inside the throughholes 2 and 3 such that each of the inner conductors 7 and 8 is electrically insulated from the part of the outer conductor 9 on the front surface la but remains electrically connected to the part of the outer conductor 9 on the back surface 1b of the block 1. The input and output electrodes 10 and 11 are coupled capacitively with the inner conductors 7 and 8, respectively. Two dielectric coaxial resonators of one-open-end-and-one-short-circuited-end type are thus formed in the dielectric block 1. Such a prior art method of forming electrodes, as described above, is very troublesome to carry out because it includes a resist-forming process for forming the resist films 4 and 5 and a resist-removing process for removing them. The resist-forming process is particularly troublesome because two resist films 4 and 5 must be formed separately on the edge between the top surface 1c and the right-hand side surface 1d and the opposite edge between the top surface 1c and the left-hand side surface 1e. Productivity by such a prior art method, therefore, was very low.
In addition, the prior art method as described above makes it necessary to complete the patterning of the resist films 4 and 5 before the conductive film 6 and the inner conductors 7 and 8 are formed. Thus, the patterns and the positions of the input and output electrodes cannot be changed easily.